Grid'5000 experiment

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Fixing the Linux implementation of the TCP CUBIC congestion avoidance algorithm (Networking)

Conducted by

Lucas Nussbaum


The TCP CUBIC algorithm, which is the default congestion avoidance algorithm since Linux 2.6.19, gained a new set of heuristics called HyStart in Linux 2.6.29[1]. This algorithm uses RTT and ack spacing measurements to decide when to exit slow start. However, experiments on Grid'5000 demonstrated very poor performance in some cases[2]. We proposed some patches[3] to improve the behaviour of Linux, and after more discussion, another set of patches[4] was proposed and applied to Linux. The fixes will be available in Linux 2.6.39, and are likely to be backported to stable kernel versions. [1]Sangtae Ha and Injong Rhee.Taming the Elephants: New TCP Slow Start, NCSU TechReport 2008. [2] [3] [4]




  • Nodes involved: 10
  • Sites involved: 2
  • Use kadeploy: yes
  • CPU bound: no
  • Memory bound: no
  • Storage bound: no
  • Network bound: yes
  • Interlink bound: yes

Tools used

No information


Not yet

Shared by: Lucas Nussbaum
Last update: 2011-06-15 17:18:04
Experiment #718